Sanitary paper tissue and towel products are widely used. Such items are commercially offered in formats tailored for a variety of uses such as facial tissues, toilet tissues and absorbent towels.
In order to be consumer preferred, the tissue/towel product needs to be aesthetically pleasing. The aesthetically pleasing tissue paper is typically an embossed substrate. Embossing of webs can provide improvements to the web such as increased bulk, improved water holding capacity, improved aesthetics and other benefits. Both single ply and multiple ply (or multi-ply) webs are known in the art and can be embossed. Multi-ply paper webs are webs that include at least two plies superimposed in face-to-face relationship to form a laminate.
During a typical embossing process, a web substrate is fed through a nip formed between juxtaposed generally axially parallel rolls. Embossing elements on the rolls compress and/or deform the web. If a multi-ply product is being formed, two or more plies are fed through the nip and regions of each ply are brought into a contacting relationship with the opposing ply. The embossed regions of the plies may produce an aesthetic pattern and provide a means for joining and maintaining the plies in face-to-face contacting relationship.
Embossing is typically performed by one of two processes; knob-to-knob embossing or nested embossing. Knob-to-knob embossing typically consists of generally axially parallel rolls juxtaposed to form a nip between the embossing elements on opposing rolls. Nested embossing typically consists of embossing elements of one roll meshed between the embossing elements of the other roll. Examples of knob-to-knob embossing and nested embossing are illustrated in the U.S. Pat. Nos. 3,414,459; 3,547,723; 3,556,907; 3,708,366; 3,738,905; 3,867,225; 4,483,728; 5,468,323; 6,086,715; 6,277,466; 6,395,133; and, 6,846,172 B2.
Knob-to-knob embossing generally produces a web comprising pillowed regions which can enhance the thickness of the product. However, the pillows have a tendency to collapse under pressure due to lack of support. Consequently, the thickness benefit is typically lost during the balance of the converting operation and subsequent packaging, diminishing the quilted appearance and/or thickness benefit sought by the embossing.
During the embossing process, the plies are fed through a nip formed between juxtaposed axially parallel rolls. Embossment knobs on these rolls compress like regions of each ply into engagement and contacting relationship with the opposing ply. The compressed regions of the plies produce an aesthetic pattern and provide a means for joining and maintaining the plies in face-to-face contacting relationship.
Nested embossing has proven to be the preferred process for producing products exhibiting a softer more quilted appearance that is maintained throughout the balance of the converting process including packaging. With nested embossing, one ply has a male pattern, while the other ply has a female pattern. As the two plies travel through the nip of the embossment rolls, the patterns are meshed together. Nested embossing aligns the knob crests on the male embossment roll with the low areas on the female embossment roll. As a result, the embossed sites produced on one ply provide support for the embossed sites on the other ply.
The nested embossment rolls may be designed such that the knobs on one roll contact the periphery of the other embossing roll providing a lamination point, thereby eliminating the need for a marrying roll. Such nested embossing arrangement is shown in U.S. Pat. No. 5,468,323 issued Nov. 21, 1995 to McNeil. This arrangement also provides a means for improving the bond strength between the plies by enabling a glue applicator roll to be used in conjunction with each of the embossment rolls providing an adhesive joint at each of the embossed sites.
Consumer testing of products having embossed cellulosic fibrous structures has determined that a softer, more quilted appearance is desired. Consumers desire products having relatively high caliper with aesthetically pleasing decorative patterns exhibiting a high quality cloth-like appearance. Such attributes must be provided without sacrificing the products' other desired qualities of softness, absorbency, drape (limpness) and bond strength between the plies.
Different attempts have been made in the art to produce paper products exhibiting superior functional properties as well as aesthetically pleasing decorative qualities. The present invention provides an embossed multiple ply tissue where the embossment patterns on each of the two plies are designed with specific objectives in mind. For instance, the embossed pattern on the first ply is based primarily on aesthetics while the embossed pattern on the second ply is based primarily on functional properties such as thickness and strength. In addition, the quantity and locations of the connections between the two plies are limited in order to coordinate the bond strength between the two plies with softness and drape of the final product. Another type of embossing, deep-nested embossing, has been developed and used to provide unique characteristics to the embossed web. Deep-nested embossing refers to embossing that utilizes paired emboss elements, wherein the protrusions from the different embossing elements are coordinated such that the protrusions of one embossing element fit into the space between the protrusions of the other embossing element. Although many deep-nested embossing processes are configured such that the embossing elements of the opposing embossing members do not touch each other or the surface of the opposing embossing member, embodiments are contemplated wherein the deep-nested embossing process includes tolerance such that the embossing elements touch each other or the surface of the opposing embossing member when engaged. (Of course, in the actual process, the embossing members generally do not touch each other or the opposing embossing member because the web is disposed between the embossing members.) Exemplary deep-nested embossing techniques are described in U.S. Pat. Nos. 5,686,168 and 5,294,475.
Accordingly, it would be desirable to provide an embossed tissue product that is more aesthetically pleasing than prior attempts. It is believed that managing the amount of embossments that are provided as ‘dots’ and those provided as ‘line art’ provide just this consumer appeal. Alternatively, providing an embossed tissue product with a known embossment ‘footprint’ can also provide significant consumer appeal.